1. Field of the Invention
The present invention relates to a charging cable, a charging control device, and a vehicle charging system for charging a vehicle-driving power storage device provided in a vehicle.
2. Description of the Related Art
Attention has been given in recent years to environment-conscious vehicles such as electric vehicles, hybrid vehicles, and fuel cell vehicles. These vehicles are equipped with electric motors for generating power to drive the vehicles and power storage devices for storing power supplied to the electric motors. Hybrid vehicles are further equipped with internal combustion engines as power sources in addition to the electric motors, while fuel cell vehicles are equipped with fuel cells as vehicle-driving DC power sources.
Some of the foregoing vehicles are known to be able to charge the vehicle-driving power storage devices by domestic power sources. For example, power is supplied from the domestic power source to the power storage device through a charging cable connected between a receptacle of commercial power source in a residential house and a charging port of the vehicle. Those vehicles capable of charging the on-board power storage devices by external power sources are referred to as “plug-in vehicles.”
Japanese Unexamined Patent Publication No. 1997-161882 discloses a structure of a charging connector of an electric automobile.
Standards for the plug-in vehicles are established in the United States by “SAE Electric Vehicle Conductive Charge Coupler” (November 2001) according to SAE International standards, and in Japan by “General Requirements for Electric Vehicle Conductive Charging System (Mar. 29, 2001)” in Japan Electric Vehicle Association Standard (Japan Electric Vehicle Standard).
“SAE Electric Vehicle Conductive Charge Coupler” and “General Requirements for Electric Vehicle Conductive Charging System” define standards regarding, for example, control pilot.
The control pilot is defined as a control line connecting a control circuit for EVSE (Electric Vehicle Supply Equipment), which supplies power from a premises wiring to the vehicle, and a ground portion of the vehicle through a vehicle-side control circuit. A pilot signal transmitted through the control line is used as a basis for, for example, detecting the state of connection of the charging cable, determining whether power can be supplied from the power source to the vehicle, and detecting the rated current of the EVSE.
However, “SAE Electric Vehicle Conductive Charge Coupler” and “General Requirements for Electric Vehicle Conductive Charging System” do not particularly define details of how to detect a break of the control line through which the pilot signal is transmitted.
For example, when the potential of the control line is at ground level, this cannot be differentiated between a break of the control line, failure of the power source, unintentional disconnection of the charging cable off the receptacle, and other causes.
Thus, when the charging cable is connected but the power storage device is not charged, the user is not aware of this situation until the power storage device is in a discharged state. This forces the hybrid vehicles to run only on fuel such as gasoline to the detriment of mileage.
The pilot signal is a requisite signal for controlling charging of plug-in vehicles. It is therefore vital to detect abnormality in the pilot signal, especially a break of the control line through which the pilot signal is transmitted.